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Question: River Murray Flood, Fish Kills

The Hon. T.A. FRANKS (15:29): I seek leave to make a brief explanation before asking the Minister for Primary Industries and Regional Development a question about mass fish kills in the Murray.

Leave granted.

The Hon. T.A. FRANKS: Biosecurity is the lead agency for coordinating the response of our state to fish-kill incidents, while PIRSA, fisheries and aquaculture may also be involved in any reactions to a fish kill, although I will note that, in terms of the clean-up, the lead agency is to be determined at the time and is currently undetermined.

In late 2022 and early 2023, there were widespread reports in South Australia of dead fish washing up on the banks of the river, from Walker Flat and Mypolonga near Mannum to Milang on Lake Alexandrina and Goolwa Beach at the Murray Mouth. Waters from last year's floods are gushing out to sea and the salinity of the ocean has been lethal, leading to dead fish washing up on our beaches.

That was as the floodwaters rose. Now, as they recede, we have seen in recent days, interstate, millions of fish dying in the lower Darling-Baaka River near Menindee in New South Wales. In fact, it was the 31st such recorded incident since July 2022 and certainly the largest such incident in recorded data for this state. Indeed, while we talk about fish kills, the numbers are usually in the hundreds or the tens, sometimes the thousands, but certainly not as we have seen: in the tens of thousands.

An emergency response has of course been put into action in New South Wales, in the state's far west, to coordinate the clean-up of the worst mass kill to ever hit that region, with fears it could cause an ecological disaster that will take years for the river to recover from. Photos supplied by Menindee residents showed dead fish, mostly bony bream but also Murray cod, golden perch, silver perch and carp, blanketed across the river's surface. This incident is just the latest in a series of large-scale fish deaths that have prompted questions about the management of our Murray-Darling Basin. Those photos certainly do not convey the stench.

These are clearly not standalone events. Impacts of climate change, pollution and flash flooding have caused the deaths of these fish and significant impacts to the residents of the Riverland. While fish deaths in smaller numbers of 100 to 500 are to be expected, there seems to be nothing 'natural' about close to a million fish dying in a single incident. The New South Wales Department of Primary Industries' fisheries arm has been dispatching officers to assist with the fish-kill assessment and community discussions and clean-up. My questions to the minister are:

1. Can the minister update the council on the number and nature of fish kills in our state in the last six months as the rivers have risen?

2. Also, what preparations are being made?

3. What monitoring is being done now that the floodwaters are receding?

4. What learnings are being taken from the significant mass fish-kill incident in our neighbouring state of New South Wales to ensure that we are prepared, should such an ecological disaster befall us?

The Hon. C.M. SCRIVEN (Minister for Primary Industries and Regional Development, Minister for Forest Industries) (15:32): I thank the honourable member for her very important question. The Department of Primary Industries and Regions (PIRSA) is the lead agency for the coordination of any large-scale fish-kill clean-ups if they occur in South Australia as a result of flooding. As the member mentioned, a fish-kill event is occurring in the Darling River near Menindee. Large numbers of bony herring, potentially hundreds of thousands, are being affected, as well as native fish, such as Murray cod and golden perch.

I am advised that this event is likely caused by low dissolved oxygen levels in the water in areas where floodwaters are receding. This is known as hypoxia. High air temperatures increase the risk of further reductions in dissolved oxygen and the potential for further fish-kill events. Fish kills have also occurred in the Darling River upstream, in Pooncarie, as a result of poor-quality flood plain water returning to the main channel.

High flows have led to successful recruitment events, resulting in a large biomass of fish congregating in the Darling River between Lake Wetherill and Menindee. Water for the environment is being delivered to reduce the risk of fish deaths by releasing oxygenated water from Lake Menindee. However, I am advised that this will take several weeks to pass along the system.

Fish-kill events are common throughout the Murray-Darling Basin and are often associated with hypoxia. It's expected that water from the Darling will mix with water from the Murray prior to entering South Australia. I am advised that it is unlikely that this event will result in fish kills occurring in South Australia.

In terms of information about fish kills in South Australia, as members would be aware flooding may cause blackwater and fish kills to occur. As of 17 March (last week), there was no blackwater present in the South Australian section of the River Murray. PIRSA monitors the dissolved oxygen levels of the River Murray using the Department for Environment and Water data loggers, which are located along the river, and dissolved oxygen level is a key indicator of stressful conditions.

Upstream areas of the River Murray in South Australia are experiencing conditions that are not stressful for fish, is the advice that I have. As the river level drops, water draining off the flood plains and back into the main river system may bring water that is low in oxygen back into the system, which may result in fish kills in the main river channel.

PIRSA has an operational response plan in place and coordinates clean-up operations and the disposal of fish carcasses for large-scale fish-kill incidents associated with flooding of the River Murray in 2023. Clean-up operations mitigate the risk of adverse socio-economic, human health and environmental impacts. The need for clean-up works is assessed on a case-by-case basis and will consider factors such as the numbers of dead fish and proximity to towns and tourist attractions.

Along with PIRSA, I would encourage members of the public to contact Fishwatch on 1800 065 522 if they notice anything unusual along the river here in South Australia.

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